[Cybsled]

Lorewise, the great sundering is also known as the Cataclysm. Blizzard always planned to add Queen Azshara at somepoint (the untextured temple was included with the Vanilla files) and she, as has been said, pretty much one of the last top dogs after Arthas gets owned. Sargeras' Tomb is also in the Maelstrom.

With Azshara's fight, I highly suspect mind control will play a part! Anyways, there's alot of islands in the Maelstrom area so they can do a ton of non-underwater stuff: The Sargeras tomb, the Temple of Azshara, Goblinland, that one island mentioned in the War of the Ancients book with -extremely- ancient undead that pre-date the Burning Legion, old Night Elf ruins, orcs, trolls, murlocs, etc.